PORTLAND, Maine (NEWS CENTER) -- Recent changes to state and local marijuana policies have some members of law enforcement concerned that they could see an increase in the number of drug-impaired drivers.

"People are already doing it," stated Cumberland County Sheriff Kevin Joyce. "When it was illegal people were already doing it as well."

Before he became sheriff, Joyce was a highly trained drug recognition expert, and was often called upon to assist other officers in helping them determine not only if a someone was impaired, but what drug they had taken.

When a driver is suspected of being drunk, police officers have tools to help them make that determination, with drugs it often requires an intensive investigation.

"It is highly technical," he explained. "You are playing with people's lives if you will. You know, it is real clear when somebody is under the influence and they are over a .08, they are drunk or not. With drugs, you have to be able to articulate the impairment, what the person is showing for signs and symptoms, and then differentiate what drug category they are under the influence of."

He says it does not matter if someone has a prescription for marijuana, or any other medication, if they are behind the wheel and impaired, it is against the law.

"The marijuana card basically says they can have the marijuana legally, that is all it does," said Joyce. "If you have taken the medication, you are impaired, then it is against the law. You are in danger of killing yourself or somebody else."

Scott Gagnon, a substance abuse prevention manager with Healthy Androscoggin, says studies of other states where marijuana rules have been relaxed have shown unintended consequences on the roadways. Washington state legalized the recreational use of marijuana in 2012.

"They are on pace to have a 50% increase in the number of marijuana impaired driving cases compared to the prior year," said Gagnon. "It is just not worth the risk. It is best just not to operate a vehicle if you have been under the influence."

He says he also worries that changes in attitudes towards marijuana are giving kids the wrong impression that the drug is ok to use.

"There are some significant impacts to youth and adults, and we want to make sure youth and parents are aware of the impacts of the drug," he said.